Firmware embedding techniques

  Firmware embedding techniques for a non-OS based embedded system are given below: 

1. Out of circuit programming 

2. In System Programming 

3. In Application Programming 

Out-of-Circuit Programming

• Out-of-circuit programming is performed outside the target board.
• The processor or memory chip into which the firmware needs to embedded is taken out of the target board and it is programmed with the help of programming device.
• A programming device is a dedicated unit when contains the necessary hardware circuit to generate the programming signals.
• The programmer contains a ZIF socket with locking pin to hold the device to be programmed.
• The programming device will be under the control of a utility program running on a PC.
• The programmer is interfaced to the PC through RS-232C/USB/Parallel Port Interface.
• The commands to control the programmer are sent from the utility program to the programmer through the interface.

In System Programming (ISP) 

• In ISP, programming is done within the system.
• The firmware is embedded into the target device without removing it from the target board.
• It is a flexible and easy way of firmware embedding.
• The only pre-requisite is that the device must have an ISP support.
• Apart from target board, PC, ISP utility and ISP cable, no other additional hardware is required for ISP.
• In order to perform ISP operations, the target device should be powered up in a special ‘ISP mode’.
• ISP mode allows the device to communicate with an external host through a serial interface, such as a PC or terminal.
• The device receives commands and data from the host, erases and reprograms code memory according to the received command.
• Once the operations are completed, the device is re-configured so that it will operate normally.

In Application Programming (IAP) 

• In Application Programming (IAP) is a technique used by the firmware running on the target device for modifying a selected portion of the code memory. 
• It is not a technique for the first time embedding of user written firmware. 
• It modifies the program code memory under the control of the embedded application. 
• Updating calibration data, look-up tables, etc., which are stored in the code memory, are typical examples of IAP. 
• The Boot ROM resident API instructions which perform various functions such as programming, erasing and reading the Flash memory during ISP mode is made available to the end-user written firmware for IAP. 

Firmware Embedding techniques for Operating System based Devices

Use of factory-programmed chips.

• It is used for mass production applications and reduces product development time.
• It Can‟t be used if firmware undergoes frequent changes.